Why Revision by a Second Person Is the Signature Requirement of ISO 17100

If you work with ISO 17100 or audit translation service providers, you will quickly discover that one requirement stands above all others as the defining feature of the standard. Revision by a second qualified person is not simply one step among many in the ISO 17100 workflow. It is the requirement that separates a certified translation service from an uncertified one, and the reason organisations pursue ISO 17100 certification in the first place. Understanding why this rule exists, what it demands in practice, and how auditors verify it is essential for anyone involved in translation quality management.

This article explains the revision requirement in depth, covers what the standard actually says, explores why the second person rule matters so much, and gives you practical guidance on how conformity is demonstrated and audited.

What ISO 17100 Actually Says About Revision

ISO 17100 defines revision as the bilingual examination of a translation against its source text to check that the translation is suitable for the agreed purpose. This is clause 5.3.1 of the standard. The key word here is bilingual. Revision requires someone who can read both the source and target languages and compare the two texts systematically.

The standard then goes further. Clause 5.3.1 explicitly states that revision shall be performed by a person other than the translator who produced the translation. This is the second person rule. It is not a recommendation. It is a shall statement, which in ISO terminology means it is a mandatory requirement.

The reviser must also meet the competence requirements set out in clause 3.1.4 of the standard. That means the reviser must have the same level of qualification as the translator: either a relevant degree in translation or related discipline, or a combination of education and experience that demonstrates equivalent competence. You cannot simply assign any bilingual employee to perform revision. The person must be demonstrably qualified.

For a closer look at how the standard defines and distinguishes the roles of translator, reviser, reviewer and project manager, the article on Reviser, Reviewer and Project Manager Competence Requirements in ISO 17100 covers this in detail.

Why a Second Person? The Logic Behind the Requirement

To understand why ISO 17100 insists on a second person, you need to think about how errors occur in translation and why self review is structurally unreliable.

The Self Review Problem

When a translator reads their own work, they tend to read what they intended to write rather than what they actually wrote. This is a well documented cognitive phenomenon. The brain fills in gaps, corrects errors automatically, and skips over omissions because it already knows what the text is supposed to say. The same problem affects any professional who reviews their own output, whether that is a software developer checking their own code, an engineer reviewing their own calculations, or a writer proofreading their own article.

In translation, this problem is compounded by the fact that the translator is working across two languages simultaneously. Their attention is divided between the source meaning, the target language expression, and the technical or subject matter content. By the time they have produced a translation, they are deeply embedded in their own interpretation of the source. A fresh pair of eyes from someone who has not been involved in the translation process is far more likely to catch errors, omissions, mistranslations, and inconsistencies.

The Independence Requirement as a Quality Safeguard

The requirement for a different person is not about distrust of the translator. It is a structural quality control measure. ISO 17100 is built on the principle that translation quality cannot be reliably self certified. This is consistent with how quality management works across many other industries. ISO 9001 requires internal audits to be conducted by persons who do not audit their own work. ISO 17025 requires second person review of test reports in many contexts. The principle is the same: independence at the checking stage catches what the person doing the work cannot see in their own output.

For translation specifically, the consequences of undetected errors can be significant. Legal documents with mistranslated terms can create contractual disputes. Medical translations with incorrect dosage or procedure information can endanger patients. Technical manuals with inaccurate instructions can cause equipment damage or injury. The second person revision requirement exists because the stakes in professional translation are real.

What the Reviser Is Actually Checking

ISO 17100 does not leave the content of revision undefined. The standard specifies what the reviser must check. Understanding this list helps both translation service providers design their revision process and auditors know what to look for when verifying conformity.

Mandatory Checks During Revision

The reviser must check the following aspects of the translation against the source text:

• Terminology: Is the correct terminology used consistently throughout, including any client specified terminology from glossaries or term bases?
• Register: Does the translation use the appropriate level of formality, technical language, or tone for the intended audience and purpose?
• Coherence and cohesion: Does the text flow logically? Are sentences and paragraphs connected appropriately?
• Completeness: Has all content from the source been translated? Are there any omissions?
• Accuracy: Does the translation accurately convey the meaning of the source text?
• Style: Is the style appropriate for the document type and target audience?
• Spelling, grammar and punctuation: Are these correct in the target language?
• Formatting: Does the translation preserve the formatting conventions of the source where required?
• Target locale: Is the translation appropriate for the specific target locale, including date formats, units of measurement, and cultural conventions?

This is a comprehensive checklist, and it makes clear that revision is not a light pass over the text. It is a systematic bilingual examination. A reviser who simply reads the target text without referring back to the source is not performing revision as defined by ISO 17100.

How Revision Differs From Proofreading and Review

One of the most common misunderstandings in ISO 17100 implementation is confusing revision with proofreading or review. These are different activities, and the standard treats them differently.

Revision

Revision is bilingual. The reviser works with both the source and target texts simultaneously. It is mandatory under the standard for all translations within scope. It must be performed by a qualified second person.

Proofreading

Proofreading is monolingual. The proofreader reads only the target text for language quality, without reference to the source. ISO 17100 does not make proofreading mandatory. It is an optional additional service that may be specified in the project agreement. A translation service provider that substitutes proofreading for revision is not conforming to the standard.

Review

Review is also an optional service under ISO 17100. It involves a subject matter expert examining the translation for suitability in a specific domain, such as legal, medical, or technical content. The reviewer does not need to be a qualified translator but must have expertise in the relevant field. Review is not a substitute for revision.

This distinction matters enormously for auditors. When you are auditing an ISO 17100 certified translation service provider, you need to verify that what they call revision actually meets the definition in the standard. A provider who labels their proofreading step as revision is not conforming to clause 5.3.1, even if they have documented the step in their procedure.

The article on Review and Proofreading Under ISO 17100: When Are They Actually Required? explores these distinctions further and explains when organisations choose to add these optional steps.

The Competence of the Reviser: Why It Cannot Be Delegated Casually

The second person rule only delivers its intended quality benefit if the second person is actually qualified to perform revision. ISO 17100 is explicit about this. The reviser must meet the competence requirements in clause 3.1.4, which mirror those for translators.

Qualification Pathways for Revisers

A reviser must demonstrate competence through one of the following pathways. First, a university degree in translation from a recognised institution. Second, a university degree in a relevant subject combined with at least two years of professional translation experience. Third, at least five years of professional translation experience without a relevant degree.

The 2017 amendment to ISO 17100 updated how these pathways are defined and applied, but the core principle remains: revision is a skilled professional activity, not an administrative check. A bilingual project coordinator with no translation training does not qualify as a reviser under the standard.

This is where many smaller translation service providers struggle. If they have a small team, finding a second qualified translator to review every project can be operationally challenging. Some providers address this through freelance reviser networks. Others build revision into their project allocation process from the outset. Either approach can work, but the provider must be able to demonstrate that the person performing revision meets the competence criteria.

Documenting Revision: What Records Must Exist

Conformity to ISO 17100 clause 5.3.1 is not just about having a revision process. It must be documented. The standard requires that revision is recorded as part of the project documentation. This means the provider must be able to show, for any given project, who performed the revision, when it was performed, and what the outcome was.

What Auditors Look For in Revision Records

When auditing an ISO 17100 certified provider, the auditor will typically want to see the following evidence for a sample of completed projects:

• The name of the translator and the name of the reviser, confirming they are different people
• Evidence that the reviser meets the competence requirements, such as a CV, qualification records, or an entry in the competence register
• A record that revision was completed, which may be a signed revision form, a tracked changes document, or an entry in the project management system
• Any revision comments or changes made, showing that the bilingual check actually occurred rather than being rubber stamped

A revision record that simply shows a name and a date, with no evidence of any changes or comments, can raise questions about whether genuine revision occurred. Auditors will often ask revisers to walk them through how they conduct revision on a typical project, what they check, and how they record their work. This interview evidence helps confirm whether the documented process reflects actual practice.

Common Nonconformities Related to the Revision Requirement

In practice, ISO 17100 audits regularly surface nonconformities related to the revision requirement. Understanding the most common issues helps providers avoid them and helps auditors know where to focus their sampling.

The Same Person Translating and Revising

This is the most direct violation of clause 5.3.1. It sometimes occurs in small providers where a single translator handles a project end to end. It can also occur in larger organisations where the revision step is assigned to the translator by mistake in the project management system. Any evidence that the translator and reviser are the same person is a clear nonconformity.

Unqualified Revisers

A provider may have a genuine two person process but assign revision to someone who does not meet the competence requirements. This might be a bilingual project manager, a junior linguist without sufficient experience, or a subject matter expert who is not a qualified translator. The revision step exists, but it does not conform to the standard because the reviser is not competent to perform it.

Revision Performed on the Target Text Only

If the reviser works only in the target language without comparing back to the source, they are performing proofreading, not revision. This can be difficult to detect from records alone, which is why auditor interviews with revisers are valuable. Ask the reviser to describe their process. If they describe reading the target text for fluency without systematic comparison to the source, that is not revision as defined by ISO 17100.

No Records of Revision

Some providers perform genuine revision but fail to document it adequately. Without records, an auditor cannot verify conformity. The absence of documented evidence is itself a nonconformity against the documented information requirements of the standard.

Why This Requirement Defines the Standard's Value Proposition

ISO 17100 covers many aspects of translation service delivery, from pre production activities like project agreements and source text analysis, through production steps including translation and revision, to post production activities like feedback handling and archiving. But the revision requirement is the one that most clearly defines what ISO 17100 certification means for clients.

When a client commissions a translation from an ISO 17100 certified provider, they are buying a guarantee that a qualified second person has systematically checked the translation against the source text before delivery. That guarantee is the core of the standard's value. Every other requirement in ISO 17100 supports the delivery of a quality translation, but the revision requirement is the one that verifies the translation before it leaves the provider.

This is why certification bodies focus so heavily on revision when auditing ISO 17100 providers. It is the requirement most likely to be compromised under commercial pressure, most likely to be misunderstood in implementation, and most critical to the quality outcomes the standard is designed to achieve.

If you are involved in auditing translation service providers or working in a translation business pursuing certification, understanding the full workflow that surrounds revision is equally important. The article on Translation, Check, Revision, Verification: The Four Required Stages of ISO 17100 gives a complete picture of how revision fits within the mandatory production process.

Practical Advice for Translation Service Providers

If you are implementing or maintaining ISO 17100 certification, here are the practical steps that will keep your revision process audit ready.

• Maintain a competence register for all revisers. This should include their qualifications, experience records, and the language pairs they are approved to revise. Update it whenever you add new revisers or when existing revisers gain additional qualifications.
• Assign translator and reviser at the project planning stage. Do not leave revision assignment to the end of a project. Build it into your project management workflow so that no project can be marked complete without a confirmed reviser who is different from the translator.
• Use your project management system to enforce the two person rule. If your system allows the same person to be assigned as both translator and reviser, fix that. A system control is more reliable than relying on individuals to remember the rule under deadline pressure.
• Keep revision records that show actual work was done. Tracked changes, revision comments, or a structured revision checklist with notes are far more convincing than a blank form with a signature. Even if the translation is excellent and requires few changes, the reviser should record that the check was completed and note what was examined.
• Train revisers on what ISO 17100 revision requires. Not every qualified translator automatically knows what systematic bilingual revision looks like in practice. Make sure your revisers understand the full checklist of what they are required to check and how to document their work.

Practical Advice for Auditors

If you are auditing an ISO 17100 certified translation service provider, the revision requirement deserves careful attention in your audit planning and evidence gathering.

• Sample completed projects and trace the revision records. For each sampled project, confirm that the translator and reviser are different people, that the reviser is listed in the competence register, and that a revision record exists with meaningful content.
• Interview revisers directly. Ask them to describe their revision process step by step. Ask what they do when they find an error. Ask how they record their work. The answers will tell you whether the documented procedure reflects actual practice.
• Check the competence register against the revision records. If a project shows a reviser who is not in the competence register, or whose register entry does not cover the relevant language pair, that is a finding worth pursuing.
• Do not accept proofreading as revision. If the provider describes a process where someone reads the target text for quality without systematic comparison to the source, clarify whether this is their revision step or an additional proofreading step. If it is presented as revision, it is a nonconformity.
• Look at how revision is handled under deadline pressure. Ask about what happens when a project is urgent. If the answer suggests that revision is sometimes skipped or abbreviated when time is short, that is a systemic risk worth investigating further.

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